1. Field of the Invention
The present invention relates generally to a television receiver using a synchronous detector, and is directed more particularly to a television receiver which employs a common reference oscillator to carry out both automatic fine tuning (AFT) and synchronous detection.
2. Description of the Prior Art
U.S. Pat. No. 3,750,029 discloses a television receiver which uses a single reference oscillator to accomplish both automatic fine tuning (AFT) and synchronous detection of a video signal. A phase detector in a phase locked loop (PLL) compares the phases of the reference oscillator signal and a video intermediate frequency signal to generate a control signal which, when applied to the reference oscillator, achieves coincidence between the frequencies and/or phases of the two signals. In the identified patent, the output of the phase detector applied to the reference oscillator includes relatively high frequency components to provide a short lock-in time of the PLL. However, this permits the frequency of the reference oscillator to be varied faster than is desirable for good detection by the synchronous detector.